The term “bulb” describes various underground storage organs—true bulbs, corms, tubers, and rhizomes—planted in the spring for summer and fall color. These spring-planted varieties, such as dahlias, gladiolus, and canna lilies, differ from fall-planted bulbs (tulips, daffodils) that require a cold dormancy period. Successful summer blooms depend on executing specific planting and initial care requirements during the spring season.
Selecting the Right Location and Timing
Planting time is determined by the local climate, specifically the date of the last expected hard frost. Planting should occur once the danger of freezing temperatures has passed, typically from mid-spring onward, ensuring tender roots are not damaged. Soil temperature is a more accurate indicator than air temperature; most summer bulbs perform best when the ground temperature has warmed to at least 60 degrees Fahrenheit.
Most summer-blooming varieties thrive in full sun, requiring at least six to eight hours of direct sunlight daily to support large, energy-demanding flowers. The soil must be well-drained, as prolonged exposure to standing water will cause the underground structures to rot. If your garden has heavy clay soil, amend the planting area by mixing in generous amounts of organic matter, such as compost or peat moss, to improve aeration and drainage.
Step-by-Step Bulb Installation
Once the site and timing are correct, installation requires precision regarding depth and orientation. A general rule for planting depth is to place the bulb so the base is two to three times the height of the bulb deep in the soil, which provides insulation and stability for emerging stems. Specific varieties like dahlia tubers and begonia corms are often planted much shallower, just below the surface.
Before placing the bulb, loosen the soil at the bottom of the hole and incorporate a small amount of a high-phosphorus supplement, such as bone meal or specialized bulb food. Since phosphorus is relatively immobile in the soil, adding it directly beneath the bulb ensures developing roots have immediate access to this nutrient, essential for strong root development and flower bud formation. Ensure the bulb is oriented correctly, with the pointed end facing upward toward the soil surface.
For corms or tubers that lack a distinct point, identify the slightly concave or indented side where the sprouts will emerge, and place that side facing up. After setting the bulb, gently cover it with the excavated soil, making sure not to compact the earth forcefully, which can restrict root growth. Instead, lightly firm the soil with your hand to remove large air pockets, ensuring good contact between the soil and the bulb’s surface.
Essential Initial Watering and Feeding
Immediately after planting, a thorough and deep watering is necessary to settle the soil around the bulb and eliminate any remaining air pockets. This initial moisture encourages the bulb to break dormancy and develop a robust root system. Maintain a consistent watering schedule, keeping the soil evenly moist but never saturated, until the first green shoots break the surface.
Once the foliage begins to emerge, this signals that the bulb has established its root system. At this stage, apply the first feeding of a balanced, low-nitrogen fertilizer, such as one with an N-P-K ratio around 5-10-10. The lower nitrogen content prevents excessive, weak leaf growth, while the higher proportion of phosphorus and potassium supports sturdy stems and abundant flowering.
To conserve moisture and maintain a consistent soil temperature, apply a two-to-three-inch layer of organic mulch over the planted area. Mulch, such as shredded leaves, wood chips, or straw, helps reduce water evaporation from the soil surface, providing a stable environment for developing roots and emerging shoots.